1. Field of the Invention
The invention relates to a skate adapted to derive motive power from the body weight of the user imposed thereon.
2. Prior Art
U.S. Pat. No. 619,370 to Wagner discloses a roller skate, in which the foot support is connected to the driving wheel by means of a flexible tension link and a ratchet and pawl combination in order to convert reciprocating vertical movement of the foot support into forward motion of the skate. The foot support is suspended by four suspension bars extending through the bottom plate of the frame of the skate. Four coil springs are arranged concentrically with the suspension bars and between the foot support and the bottom plate in order to restore the foot support to its upward position after the downward stroke. With this arrangement, there is increased friction between the suspension bars and the bottom plate, if the foot is tilted front to rear or sideways. Furthermore, the downward stroke is limited by the ground clearance of the suspension bar extending below the bottom plate of the frame.
U.S. Pat. No. 1,924,948 to Lieberenz discloses a skate, wherein a lazy tong structure forms the connection between the foot support and the frame. A rack connected to the center pivot of the lazy tong structure and extending below the bottom part of the frame during the downward stroke drives a pinion, which in turn cooperates with a sprocket and chain drive for propelling the skate. This arrangement also necessitates ground engaging wheels of relatively large diameter to provide adequate ground clearance.
Skates according to French Patent Specification No. 2,441,398 to Buran and U.S. Pat. No. 2,449,871 to Bohler employ driving arms spreading apart during the downward stroke to propel the skates. The connection of the foot support to these arms is such, that the foot support cannot easily be maintained in a pre-determined, stable, generally horizontal position during its vertical reciprocating movement.